1. Space weather phenomena in the ionosphere and their effect on GNSS
IPXX　ICAO ISTF/4 New Delhi, India, 5th to 7th February 2014
Space weather phenomena in the ionosphere and their effect on GNSS
(Presented by Japan)
SUMMARY
This paper presents a short review of major space weather phenomena observed in mid- and low-latitude ionosphere. Their effect on GNSS also mentioned.

2. Sudden Ionospheric Disturbance (SID)
SOHO/SEM
[count/s]
EUV
X-ray flux
GOES
[W/m2] 35
[TECU]
GPS
TEC
TIMED/GUVI
O, N2
[R] 10 15
UT [hour]
[Tsurutani et al., 2005]
[Tsugawa et al., 2007]

3. Sudden Ionospheric Disturbance (SID)
Amplitude
+Several 10 TECU
Depending on flare class
Time scale
Increase in several minutes
Enhancement lasts for several hours
Spatial structure
Global scale in the sunlit hemisphere
Depending on solar zenith angle
Other characteristics
HF radio absorption (Dellinger phenomena)
Possibility of loss-of-lock on GNSS signals due to solar radio burst
Effect on GNSS
Augmented GPS (due to TEC model correction error)
Loss-of-lock on GPS signals

4. Ionospheric Storm One-month Average Negative Storm Positive Storm JST
Wakkanai
Okinawa
foF2 [MHz]
JST (UT+9h)
One-month Average
Negative Storm
Positive
Storm Kp

5. Ionospehric Storm Amplitude
±Several 10 TECU compared to quiet conditions
Time scale
Several hours to several days
Spatial structure
Small spatial TEC gradient
Other characteristics
Basically occurring during and/or after magnetic storms
Effect on GNSS
Augmented GPS (due to TEC model correction error)

6. Equatorial Ionization Anomaly
20:40 JST, 23 Jan 2002
20:40 JST, 24 Jan 2002

7. Equatorial Ionization Anomaly
Amplitude
±Several 10 TECU
Time scale
Spatial structure
Large latitudinal TEC gradient
Other characteristics
Day-to-day variation is not negligible
(increase, disappearance, hemispheric asymmetry, etc)
Affected by magnetic storms
Effect on GNSS
Augmented GPS (due to TEC model correction error)

8. Storm enhanced density (SED)
[Foster et al., JGR, 2005]

9. Short summary of SED Amplitude +Several 10 to 100TECU Time scale
Several hours (?)
Spatial structure
Steep horizontal TEC gradient
Narrow in zonal direction
Extending in NW-SE direction
Other characteristics
Often observed from noon to sunset during the large geomagnetic storm
Sometimes accompanied with ionospheric irregularity
Effect on GNSS
Differential GPS
Augmented GPS (due to TEC model correction error)
Loss-of-lock on GPS signals

10. GPS-TEC Observations for Space Weather
Absolute TEC
ROTI (~10km scale irregularity)
Loss-of-Lock (~100m scale irregularity)
(21:20 JST)
12:20 UT
(21:40 JST)
12:40 UT
(22:00 JST)
13:00 UT
3D simulation of plasma bubble [Courtesy of Dr. T. Yokoyama (NICT) ]

11. Short summary of EPB Amplitude -Several 10 to -100TECU Time scale
Several 10 minutes to several hours
Spatial structure
Steep horizontal TEC gradient
Narrow in zonal direction
Extending along the magnetic field line
Other characteristics
Often observed mid- to low latitudes after the sunset.
Almost always accompanied with ionospheric irregularity
Effect on GNSS
Differential GPS
Augmented GPS (due to TEC model correction error)
Loss-of-lock on GPS signals

12. Traveling Ionospheric Disturbances (TID)
Large
-scale
TID
(LSTID)
[Tsugawa et al., JGR., 2003]
Medium
-scale
TID
(MSTID)
[Tsugawa et al., GPS solut., 2007]

13. Traveling Ionospheric Disturbances (TID)
Amplitude
A few TECU
Time scale
MS: Several 10 minutes
LS: Several hours
Spatial structure
MS: Wavelengths of several 100 km
LS: Wavelengths of 1,000 – 3,000 km, Zonally extended wavefront
Other characteristics
MS: Southwestward and Southeastward propagations in nighttime and daytime, respectively.
LS: Related with magnetic storm
Effect on GNSS
Differential GPS
Augmented GPS (due to TEC model correction error)

14. Summary of Ionospheric Space Weather Phenomena
Solar Act./
Mag. Storm
dependence
SED
Amplitude
Large
SID
LSTID
Med.
Ion. Strom
Eq. Ion. Anomaly
Small
Plasma Bubble
Lower Atm.
dependence
MSTID
Sporadic E
10km
100km
1000km
Global
Spatial Scale